Two Key Studies using MRI: Maguire (2000) & Luby et al. (2013) (SL IB Psychology)

Aim: To investigate the use of MRI brain-imaging technology to investigate spatial navigation in London black cab taxi drivers

Participants: 16 healthy, right-handed male London black cab taxi drivers who had passed ‘The Knowledge’, a test of spatial navigation, aged 32-62 years with a mean age of 44 years. They had all been taxi drivers for at least 18 months, with the highest number of years as a taxi driver at 42 years

Procedure: The participants were placed in an MRI scanner and their brains were scanned. The MRI measured the volume of grey matter in the hippocampus of each participant, and this was then compared to pre-existing scans of 50 healthy, right-handed males (the control group). Grey matter was measured using voxel-based morphemetry (VBM) which focuses on the density of grey matter and pixel counting

Results: The posterior hippocampi of the taxi drivers showed a greater volume of grey matter than that of the controls, who had increased grey matter in their anterior hippocampi compared to the taxi drivers. Maguire also carried out a correlational analysis which showed a positive correlation between volume of posterior hippocampal grey matter and length of time spent as a taxi driver

Conclusion: The posterior hippocampus may be linked to spatial navigation skills

Evaluation of Maguire (2000)

   Strengths

• • The study used a highly controlled clinical method of obtaining objective data which could then be easily compared and analysed
  • The study used a researcher who was blind to the conditions to count the pixels on the MRI images which increases the internal validity of the study

   Limitations

• • A correlation cannot show cause-and-effect so it is impossible to know whether the taxi drivers already had naturally high levels of hippocampal grey matter
  • The results are only generalisable to male, right-handed London taxi drivers

Key terms:

• Spatial navigation  
• Posterior hippocampus   
• Voxel-based morphometry  

Aim: TTo investigate whether poverty experienced in childhood is shown in delayed brain development using MRI scanning

Participants: Children who were already enrolled on a 10-year longitudinal study of Preschool Depression: 145 right-handed children from the USA. The children were categorised as living in poverty

Procedure: The children had undergone regular testing: once a year (over 3-6 years) which consisted of a series of tests aimed to measure their cognitive, emotional and social skills. The researchers also collected data on how close the children were to their caregivers as well as incidences of any negative and stressful events in their lives. Each child then had two MRI scans in which the whole brain was scanned (session 1) or just the hippocampus and the amygdala (session 2)

Results: Both the hippocampus and the amygdala showed less white and grey matter in the MRI scans. However, if the child had experienced positive care from adults there was a less negative effect on the hippocampus. Difficult and stressful life events only affected the left hippocampus

Conclusion: Poverty does appear to have a negative effect on brain development in childhood, but this can be reduced by the quality of caregiving the child experiences

Evaluation of Luby et al. (2013)

   Strengths

• • The researchers were able to check the behavioural, cognitive, and social measures against the MRI results which increases the internal validity of the study
  • The study’s longitudinal design means that real changes and comparisons across time could be made, as seen in the differences in the MRI scans

   Limitations

• • The MRI scans may have picked up differences in the brains of the children which were not the result of poverty but of other, unknown factors
  • The sample is difficult to generalise from as it only represents pre-school children living in poverty who exhibit symptoms of depression so it cannot explain how poverty may affect non-depressed children

Key terms:

• Hippocampus  
• Amygdala  
• Mediating factors